Messages in this thread | | | Date | Fri, 27 Mar 2020 11:44:50 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86: Discard .note.gnu.property sections in vDSO |
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On Thu, Mar 26, 2020 at 10:43:14AM -0700, H.J. Lu wrote: > With the command-line option, -mx86-used-note=yes, the x86 assembler
I see:
-mx86-used-note=no -mx86-used-note=yes These options control whether the assembler should generate GNU_PROPERTY_X86_ISA_1_USED and GNU_PROPERTY_X86_FEATURE_2_USED GNU property notes. The default can be controlled by the --enable-x86-used-note configure option.
Is there a plan to use this build option in the kernel in the future or all binutils will have it enabled or what's the story here?
Because I don't see -mx86-used-note used anywhere in the kernel...
> in binutils 2.32 and above generates a program property note in a note > section, .note.gnu.property, to encode used x86 ISAs and features. But > x86 kernel vDSO linker script only contains a single NOTE segment: > > PHDRS > { > text PT_LOAD FLAGS(5) FILEHDR PHDRS; /* PF_R|PF_X */ > dynamic PT_DYNAMIC FLAGS(4); /* PF_R */ > note PT_NOTE FLAGS(4); /* PF_R */ > eh_frame_hdr 0x6474e550; > } > > The NOTE segment generated by vDSO linker script is aligned to 4 bytes. > But .note.gnu.property section must be aligned to 8 bytes on x86-64 and > we get > > [hjl@gnu-skx-1 vdso]$ readelf -n vdso64.so > > Displaying notes found in: .note > Owner Data size Description > Linux 0x00000004 Unknown note type: (0x00000000) > description data: 06 00 00 00 > readelf: Warning: note with invalid namesz and/or descsz found at offset 0x20 > readelf: Warning: type: 0x78, namesize: 0x00000100, descsize: 0x756e694c, alignment: 8 > [hjl@gnu-skx-1 vdso]$ > > Since note.gnu.property section in vDSO is not checked by dynamic linker, > this patch discards .note.gnu.property sections in vDSO by adding
Avoid having "This patch" or "This commit" in the commit message. It is tautologically useless.
Also, do
$ git grep 'This patch' Documentation/process
for more details.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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